At the height of the American Revolution, seventeen-year-old Rachel must flee her home in New York City to escape the imminent British invasion. She settles with her aunt and uncle in Philadelphia, which is still free, but will soon fall into enemy hands. There, an old friend from New York, Alexander Hamilton, approaches her and asks her to become an American spy.

Rachel chooses Captain John André, a high-ranking British officer, as her target. He eventually breaks down and gives her military secrets; and Rachel, week after week, inds her way through the streets of Philadelphia every Saturday after religious services to deliver coded letters to "Will," a fellow spy. Is she being followed? Will her victim learn of her espionage? She recalls Hamilton's warning: "If caught, you will hang."